Clean up sliding sync implementation

[7w1]

Description

Fixes the bugs I've noticed using sliding sync on c10y, and seems to still work fine on morg accounts. Obviously needs more testing, but its better than the current implementation.

Maintains a slim classic sync when presence is enabled, because I can't seem to figure out how to get presence in sliding sync. Does however get rid of the large initial classic sync on first load when sliding sync is enabled.

Edit: forgot but also makes the buttons in the little bar at the bottom go up instead of down

Fixes #185
I think this also fixes SableClient/SableCall#10

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

Tests were updated with AI tests weren't changed lol

[github-actions]

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